In general, a cutting insert is fixed to a cutting tool, and the cutting tool is mounted on a machine tool and used to cut a workpiece.
A cutting insert in the related art has a polygonal shape, a corner cutting edge is formed at a vertex portion, a main cutting edge is formed at an edge where an upper surface and a lateral surface meet together, and a chip breaker is formed between the upper surface and the main cutting edge.
However, as illustrated in the attached FIG. 10B, in the case of the cutting insert in the related art, a cut chip c is discharged while grazing the chip breaker such that the chip c and the chip breaker come into contact with each other at two points (see p4 and p5).
Since the chip c and the chip breaker come into contact with each other at the two points (see p4 and p5), there is a problem in that a cutting load is high because cutting force is applied to the chip breaker in a state in which the cutting force is not reduced.
In addition, since the chip c and the chip breaker come into contact with each other at the two points (see p4 and p5), there is a problem in that the contact points may be unstable, and chip curls are not uniformly formed. If the chip curls are not uniform, the chips have different sizes, and particularly, a long chip having a long length may be formed. The long chip makes it difficult to discharge the chips.
Meanwhile, high heat is generated at the cutting insert during the cutting process. The cutting insert needs to be cooled because the high heat adversely affects a lifespan of the cutting insert. The cut chip may exchange heat while coming into contact with the chip breaker, and the discharge of the heated cut chip assists in cooling the cutting insert. However, in the case of the cutting insert in the related art, since the chip c and the chip breaker come into contact with each other at the two points (see p4 and p5), a cooling effect may not be great.